Hayes Sway Master: Master of Sway Control

A high-tech cure for trailer sway, Hayes’ electronic system applies varying braking force to the trailer’s wheels to bring it in-line

It’s the age-old dilemma that all trailerists deal with: trailer sway. It can be a real problem that ranges in severity from an annoyance to a frightening loss of control. There are a number of ways to minimize sway, but once it starts, often as the result of outside forces, it takes an immediate action on the part of the driver, or a device, to stop it.

Eye to the SkyThe Sway Master uses a GPS receiver to detect the speed of the vehicle and an inertial sensor to detect trailer sway. Combining the two technologies, the Sway Master calculates the amount of brake force to apply.

What causes sway? A number of factors can contribute to it. First is a mismatched tow vehicle and trailer. Some SUVs are poor tow vehicles, despite having high tow ratings. This is the result of a short wheelbase combined with high-profile light-duty tires, and trailers that are not balanced properly (i.e., not enough hitch weight). While the powertrain can easily handle the weight, the bouncy suspension, coupled with flex in the tire sidewalls, can allow “the tail to wag the dog,” as the saying goes.

Incorrect hitch setup is another major contributor. If a trailer rides too high in the front, it can lead to sway. Failure to use a sway-control device, or using the wrong type, can also be a factor.

Then there are the outside contributors, which include crosswinds, road crown and catching the edge of the road. When these things come into play, the first reaction many drivers have is to jerk the wheel to get back on the road, overcorrecting steering and starting the lateral movement of the trailer, which can lead to control problems. And then there are passing trucks, whose large sizes can cause air currents to push against a large, lightweight RV, leading to sway.

Installing the Sway Master may require some prep. In this case, we had to move the original seven-way cable and LP-gas line to make room. The Sway Master must have a clear view to the sky for the GPS to function, so keep it as far forward as possible. Photos by Chris Dougherty

How can we fix sway? First, of course, is to match the tow vehicle to the trailer. The longer the trailer, the more wheelbase and stiffness you’ll need in the tow vehicle. While there are a number of sway-control devices on the market, from specialty hitches to hardware that provides friction to resist the lateral movement of the trailer, Hayes Towing Electronics has developed a high-tech way of dealing with trailer sway, the Sway Master. The system electronically controls the trailer by calculating the rate of sway and applying the trailer brakes at a rate that brings the trailer back to center without drastically altering the vehicle’s speed or ride characteristics or requiring the driver to manually activate the trailer brakes.

The Sway Master is equipped with a gyroscope, or electronic inertial sensor, to determine the rate of sway, and a GPS receiver to determine vehicle speed. It uses this data to determine if a sway event is occurring and, if so, how much power to apply to the trailer brakes.

The Sway Master is a remarkably simple device to install. The trailer’s seven-way plug connects to the unit, which is mounted on the A-frame of the trailer with four self-drilling screws. The cable from the device then plugs into the seven-way receptacle on the tow vehicle. The only caveat is that the Sway Master has to be mounted in such a location that it has a clear view of the sky. The main unit has a status light on it, so when it is plugged into the tow vehicle, the driver immediately knows whether it is working or not. Parallel circuitry in the unit works in tandem with the seven-way circuitry, so there’s no wiring involved.

Installing the Sway Master is simple. Four self-drilling screws secure it to the frame.

To see how it would operate under varying circumstances, we put the Sway Master to the test on two different travel trailers towed by the same vehicle, a 2012 Ford F-350, which has a Class 5 hitch receiver and is capable of towing a trailer without weight-distribution or sway-control gear.

We had the opportunity to test the new 2017 Winnebago Minnie 2500FL trailer, which is 28 feet long and weighs around 5,300 pounds empty. Even without weight distribution or another sway-prevention device, the Minnie towed pretty compliantly. Once we got out on the interstate with no traffic around us, I put the trailer into a sway event (don’t try this at home; I’m a former professional driver). Immediately, there was a nice little tug on the truck, and the trailer came right in line. I tried again with the same result. As soon as a slight sway was detected, the Sway Master applied just the right amount of brake force to stop it.

Later on, while being passed by high-speed trucks and being influenced by slipstream currents exerted on the trailer, it was evident that the Sway Master countered the situations immediately.

The trailer’s seven-way cable plugs into the unit. The cable is routed to the front and secured using cable clips, and the LP-gas line is resecured.

We then installed the Sway Master on a 33-foot travel trailer that weighs about 10,000 pounds. This time we used a standard weight-distributing hitch without a sway control and conducted the tests in the same manner — except that we experienced winds in the 20-mph range and occasional gusts around 30 mph on Labor Day during Post-Tropical Hurricane Hermine.

Results were mixed, as we had some brief wind-driven sways that did not seem to cause the Sway Master to activate the brakes. However, we were able to get the unit to activate with some hard, intentional sway events during a controlled test. Our take on this is that, with a 33-foot trailer, the sway “feel” at the A-frame is considerably different than with the shorter Winnebago. At no time did we have a sway condition that resulted in a loss of control of the trailer.

The benefits of having the electronic device for controlling sway are threefold: First, you don’t have to apply the trailer brakes. The Sway Master does it for you.

Second, in a sway event, most people will panic and hit the tow vehicle’s brakes, and if they don’t panic, they’ll engage the trailer brake’s manual control on full. This will likely lock up the brakes, if the brake-control gain is adjusted too strongly. Based on the amount of trailer sway and vehicle speed, the Sway Master applies a calculated amount of amperage to the brakes for just the right length of time.

The Sway Master comes with a holder for the seven-way plug to keep it clean and out of the way.

Lastly, with the Sway Master, both hands remain on the wheel, maintaining full control of the vehicle.

If the trailer is prone to sway, the driver will feel a lot of tugging from the trailer as the Sway Master is activated. But it will be safe tugging and an indication that the tow-vehicle-and-trailer setup is less than ideal and needs some attention.

The Hayes Sway Master comes with a two-year limited warranty and is an accessory that every trailerist should consider. It has a $349 suggested retail price and at press time was available at Camping World at a discounted Good Sam Club member rate of $299.

Chris Dougherty is technical editor of Trailer Life and MotorHome. Chris is an RVDA/RVIA certified technician and lifelong RVer, including 10 years as a full-timer. He and his wife make their home in Massachusetts and hit the road with their travel trailer every chance they get.

2 COMMENTS

Do you ship a Hayes Swaymaster control (serial # ha81775-ofmto) to a suburb of Brisbane, Queensland, Australia? And what is the price all up to buy and ship to Australia? In all the videos I have seen of this unit, it looks good for Australian roads. Does it work on dirt outback roads? Steve Stonestreet

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